The invention relates to a hardenable composition containing
A) compounds having at least two activated double bonds (I) based on .alpha.,.beta.-unsaturated carbonyl compounds, .alpha.,.beta.-unsaturated carboxylic acid esters or .alpha.,.beta.-unsaturated nitrile groups, PA1 B) compounds containing either at least one primary amino group which is blocked by an aldehyde or ketone having not more than 10 C atoms or at least 2 groups which can be hydrolyzed to NH groups, and PA1 C) customary additives, if appropriate catalysts, if appropriate pigments and organic solvents. PA1 A) compounds having at least two activated double bonds (I) based on .alpha.,.beta.-unsaturated carbonyl compounds, .alpha.,.beta.-unsaturated carboxylic acid esters or .alpha.,.beta.-unsaturated nitrile groups, PA1 B) compounds containing either at least one primary amino group which is blocked by an aldehyde or ketone having not more than 10 C atoms or at least 2 groups which can be hydrolyzed to NH groups, and PA1 C) customary additives, if appropriate catalysts, if appropriate pigments and organic solvents, wherein either component A or component B or components A and B are based on a branched soluble acrylate copolymer P which is obtainable by copolymerization of PA1 a) 5 to 30% by weight of monomers having at least two ethylenically unsaturated polymerizable double bonds, PA1 b) 5 to 60% by weight of monomers having a functional group and PA1 c) 5 to 90% by weight of other ethylenically unsaturated monomers, the sum of a, b and c being 100% by weight.
The present invention also relates to processes for the preparation of these compositions and their use.
Compositions which are obtained by reaction of compounds having at least two activated double bonds (I) with compounds containing active hydrogen atoms are known from EP 160,824. These compositions react under the influence of bases to give a Michael addition product. The Michael acceptor component can be derived, for example, from acrylate resins containing hydroxyl groups, epoxy resins, oligomeric polyols or oligomeric polyamines. The Michael donor component can be derived, for example, from polyols, polyamines or polymercaptans The binders described in EP 160,824 can be used as two-component systems for coatings. They readily harden under catalysis of bases at room temperature and at elevated temperatures. The advantages of the systems described is that they do not require free isocyanates for hardening. However, the known systems have disadvantages in respect of the stability to solvents, resistance to chemicals and elasticity of the coatings obtained from them.
Compositions which are obtained by reaction of compounds having at least two activated double bonds with compounds which contain at least one primary amino group and are blocked by an aldehyde or ketone are known from EP 230,296. These compositions react under the influence of atmospheric moisture at various temperatures to give a Michael addition product. However, these compositions are in need of improvement in respect of the stability to solvents and resistance to chemicals of the coatings produced from them. Another disadvantage of these compositions is the high solvent content of the coating compositions caused by the high viscosity of the binder solutions, since it leads to high pollution of the environment by solvents during drying of the lacquer films.
Hardenable compositions which contain compounds A having at least two activated double bonds and compounds B having active hydrogen atoms are described in the prior, previously unpublished Patent Application DE 3, 710 431. These compositions react under the influence of bases to give a Michael addition product. At least one of the compounds A and B is based on a branched acrylate copolymer P which is soluble in organic solvents. In contrast to the present application, exclusively carbonyl compounds selected from the group comprising acetoacetic acid, cyanoacetic acid, malonic acid, cyclopentanonecarboxylic acid, cyclohexanonecarboxylic acid and the particular alkyl esters and reaction products of these carbonyl compounds with acrylate copolymers containing hydroxyl and glycidyl groups are employed as compound B. Compounds B containing amino groups are not described.
EP-A-158 161 describes coating compositions which harden at low temperatures and are based on branched acrylate copolymers containing hydroxyl groups and melamine-formaldehyde resins or polyisocyanates as crosslinking agents. 3 to 25% by weight of monomers having at least two polymerizable olefinically unsaturated double bonds are employed in the polymerization for the preparation of the acrylate copolymer. The coating agents based on the systems described have a good stability towards benzene and a good stability towards long-term exposure to water or water vapor. However, the melamine-formaldehyde resins or polyisocyanates employed as crosslinking agents have an adverse effect for toxicological reasons.
The invention was thus based on the object of providing coating compositions which can be hardened at low temperatures and therefore can preferably be employed in automobile repair lacquering and are largely free from isocyanate. In particular, these coating compositions should lead to lacquer films with--in respect of the systems of EP 160 824 and EP 230 296--improved stability to solvents and resistance to chemicals. These coating compositions should furthermore have the maximum possible solids content at a viscosity, which is favorable for processing, of 16 to 20 s, measured in a flow cup in accordance with DIN 4.degree. at 23.degree. C.